Method for obtaining well defined edge radii on cutting tool inserts by electropolishing technique

Abstract

There is disclosed a method for edge rounding of cutting tool inserts of cemented carbide or titanium based carbonitride alloys. An electrolytic method is used with an electrolyte which provides an even removal of both binder phase and hard constituent phases. The electrolyte comprises perchloric (HC10 4 ) sulphuric (H 2 SO 4 ) acid, 2-15 vol %, and mixtures thereof in methanol or other suitable organic liquid. The method is easier to control than conventional mechanical methods and is particularly useful for providing very small edge radii of about 10 μm which cannot be made by mechanical methods.

What is claimed is: 
     
       1. An electropolishing method for edge rounding of cutting tool inserts of cemented carbide or titanium based carbonitride alloys in an electrolyte comprising 2-15 volume % of an acid selected from the group consisting of perchloric (HC10 4 ) acid, sulphuric (H 2  SO 4 ) acid and mixtures thereof, in an organic liquid carrier comprising; submerging said inserts into the electrolyte;   providing an electrode of an acid resistant material within the electrolyte;   applying an electrical potential between the inserts and the electrode for a period of time sufficient to round the edges of said inserts to a desired degree.   
     
     
       2. The method of claim 1, wherein all edge rounding of about 10 μm is obtained. 
     
     
       3. The method of claim 1, wherein the organic liquid carrier is a lower alkanol. 
     
     
       4. The method of claim 3, wherein the organic liquid carrier is methanol. 
     
     
       5. The method of claim 1, wherein the electrode is made of platinum. 
     
     
       6. The method of claim 1, wherein the electrical potential is applied at a voltage of 10 to 40 volts.